1. Field of the Invention
The present invention relates to a method of printing images onto edible pieces. Most preferably, this invention relates to the method of forming multicolor images on non-planar surfaces of confectionery and pharmaceutical pieces/tablets. The invention also relates to an apparatus for practicing the method of the invention and to edible shaped pieces having a multicolor registered composite image on a non-planar surface thereof.
2. Related Background
Many edible items (“pieces”) have a sugar shell outer coating. Such outer sugar shells serve many functions, including preserving the inner ingredients and presenting an attractive exterior. Further, the outer sugar shell can serve as a substrate on which an image or design is formed. Such images or designs can be, for example, an identifying trademark such as the “M” on M&M's® Chocolate Candies pieces, or marks to identify the inner ingredients in the case of drugs or dietary supplements.
Many methods are known to form a one-color design on to an edible piece. U.S. Pat. No. 3,052,552, for example, describes a method of printing chewing gum slabs prior to the slabs being cut into sticks of individual gum pieces.
U.S. Pat. No. 5,834,047 describes a method of imprinting shapes of multiple colors inside confectionery products by partially filling and solidifying a confectionery material in a mold, dispersing edible ink onto the solidified mixture through an etched plate, and filling the remainder of the mold with confectionery material.
It would be desirable to form multicolor designs on surfaces of edible pieces, particularly non-planar surfaces, at high production speeds. Multicolor designs are conveniently produced by the application of a sequence of images, each image being a single color. The cumulative effect is of a multicolor image or design. Such multiple applications of images require that each applied image be in registry with the previously applied images and with any subsequently applied images to achieve the desired composite image. Images applied out of registry will result in smearing, skewing, overprinting, or other erroneous and faulty results.
Many multicolor printing methods are known in the graphic arts for non-food products. These methods include relief printing, stamp-printing, offset printing, pad printing, flexographic printing, gravure printing, inkjet printing, and silk-screen printing. Direct transfer of such methods to multicolor printing on edible pieces, however, is difficult—particularly for printing onto non-planar surfaces. The handling of edible pieces entails different considerations from the handling of paper or polymer sheets. Generally, edible pieces require more careful handling to prevent damage or misshaping of the pieces. Further, handling food generally require higher cleanliness.
Methods are known to perform multiple printing onto large solid articles such as bottles and other storage cylinders. U.S. Pat. No. 3,335,658 describes a machine that conveys individual articles, on a disk or endless band, through printing stations and drying stations that are placed at specific distance increments that are not evenly divisible into the periphery distances of the disk or endless band. U.S. Pat. No. 3,735,699 describes an apparatus that applies rolling contact between an article held by a mechanical holder and intermediate belt or rollers. The belt or rollers transfer images onto the contacted, mechanically held article. U.S. Pat. No. 4,519,310 describes transferring a plurality of ink onto the outer periphery of a single ink form roller, pressing a cylindrical container against the ink form roller, and rotating the cylindrical container to transfer the ink images onto the cylindrical container. The above patents are incorporated by reference herein.
Methods are also known to form multicolor images on large food items such as cakes and cookies. U.S. Pat. No. 4,578,273 describes a method of printing by forming a hard, nonporous icing surface and printing one or more edible inks onto the hard surface of the icing. Each piece is manually placed onto a moving mandrel for printing by a pan flex printer. U.S. Pat. No. 4,670,271 describes a food imprinting cassette that transfers an edible coloring material to food when pressure from a stylus is applied to the flexible transfer sheet on which is the coloring material. U.S. Pat. No. 5,534,281 describes a method of making printed foods with a rotary printer that is synchronized with a dough-forming apparatus such as a rotary cutter or rotary molder. U.S. Pat. No. 5,505,775 describes a cake decorating system incorporating a traveling arm extending over the cake surface to carry a colorant cartridge with a drop on demand colorant expulsion system under the control of a central processor. A multiple orifice drop on demand colorant expulsion system allows one pass three color printing. The above patents are incorporated by reference herein.
Other methods are known to form multicolor designs onto flat sheet surfaces of confections. International Patent Publication No. WO 97/16075 describes multicolor printing onto flat sheets of bubble gum situated in a recess having dimensions larger than that of the flat sheets of bubble gum. A guide rail is used to laterally shift the bubble gum sheets against a common side of the recess before printing, but no means are provided to prevent longitudinal shifting, skewing or yawing since the recesses are larger than the bubble gum. It is indicated that a vacuum system inside the apparatus could be used to remove excess starch that falls between the slats of the conveyor bed and that, while dedusting, this vacuum would help hold the gum sheets on the conveyor. However, there is no disclosure or suggestion of a shaped pocket that positions an edible piece in a predetermined position, both laterally and longitudinally without skewing or yawing, and that includes an opening in communication with a vacuum that maintains the registration of an edible shaped piece between a first printing station and a second printing station.
The methods presently available for printing multicolor images onto edible pieces, and particularly onto non-planar surfaces of edible pieces, are limited in their production rates. Multicolor printing on individual pieces require an alignment of each piece within the geometries of each printing step. Such alignment is known as registration. Multicolor printing requires registration in many directions. Further, unlike printing onto flat planar surfaces, printing onto non-planar surfaces requires an added registration alignment in regard to the contour of the non-planar surface. The piece must not be allowed to rock, yaw, or skew from one printing station to the next.
Generally, in mass production the multitude of pieces are moved in relation to the usually stationary print station. Many methods are known to transport pieces, as described in the above patents. U.S. Pat. No. 5,836,243, incorporated by reference herein, describes a pellet conveyor made up of a plurality of carrier bars each having a surface defining a plurality of pockets. A brush is described that facilitates seating of the pellets in the pockets.
U.S. Pat. No. 4,671,892, incorporated by reference herein, describes an apparatus for conveying and marking pellet-shaped pieces by utilizing two printing heads positioned along an arcuate transfer path about a transfer drum so as to apply single color indicia to opposite sides of the pellets. U.S. Pat. No. 5,423,252, incorporated by reference herein, describes a capsule or tablet (article) printer in which a vacuum is applied below a transporting belt to vacuum holes provided in article receiving pockets. In one embodiment, a first printing unit 110 prints on one side of the article, and another printing unit 110′ prints on a second side of the article. However, there is no disclosure of applying a vacuum at and between the first and second printing units, registering the printing between the first and second sides of the article, or of the particular vacuum holes or carrier bars.
Most designs that incorporate component images to form, in combination, a multicolor composite image, require registration in many directions besides the longitudinal direction of movement of the pieces. There must be registration transverse to the longitudinal movement direction to prevent images being inadvertently offset. There also must be registration in the third coordinate orthogonal to the longitudinal movement direction and the transverse direction. Finally, particularly important for non-planar surfaces, there should be registration in regard to any of three rotational orthogonal axes centered at each piece.
The above described methods generally require that the individual pieces be mounted in a fixture or holder that mechanically fixes each piece in registration. The manually aligned methods are too slow for mass production rates except for food items made at low throughput such as cakes. The above mechanical attachment methods also require complex components that can become misaligned, broken, or jammed at high production speeds. Further, many food items are delicate and not amenable to such mechanical forces that may be needed to maintain adequate registration of printing at high production speeds.
U.S. Pat. No. 5,534,281 produces baked goods at moderate production rates by utilizing the inherent stickiness or tackiness of the dough, which must sufficiently adhere to the continuous web conveyor in order to ensure no relevant movement between the dough and the web, for proper alignment and registration with the printing apparatus. Methods that rely on the tackiness of the individual pieces or of the conveying belt are limited in their production speed because the various production steps must be carefully controlled to avoid breaking the adhesive bond between the individual pieces and the conveying belt. Further, the production speed is constrained by diametrically opposite considerations with regard to the stickiness of the adhesive bond. Higher printing speeds require higher levels of stickiness, but higher offloading speeds require lower levels of stickiness. In other words, higher stickiness holds the pieces in position more firmly to allow higher throughput in printing but higher stickiness prevents the pieces from being released quickly after their being printed. Thus, the above methods are incapable of multicolor printing onto surfaces of edible pieces, particularly onto non-planar surfaces of edible pieces, at high production speeds.
Presently, at high speed mass production, designs applied to non-planar surfaces of edible pieces are limited to one-color designs (or multiple independent designs that can be of different colors, but are unrelated to each other) because it is very difficult to apply consecutive images in registry to non-planar surfaces of edible pieces. That is, after the application of one image, the piece shifts or moves before the application of the next image, thereby causing the images to be out of registry. Accordingly, it would be desirable to provide a method to form multiple images in registry onto surfaces of edible pieces, and particularly onto non-planar surfaces of edible pieces, at high production rates.